Aww.
Okay, so let's start with the prologue.
The “Prologue” must establish all of the musical elements that will be used throughout the piece to accustom the audience’s ears to it, and it certainly accomplishes that feat. The very first chord played in the show introduces the first important element, the major/minor triad. (cluster, A/C thing I previously mentioned). This quickly becomes the norm in the early portions of the piece, as almost every chord is built this way. Next, the tritone is heard, from the A to D-sharp in measure 12. After the second cadence in measure 18, the “Prologue” begins again with a fresh motive. (This is the part after the 2nd round of snaps, when other instruments come in after the sax solo). It sounds new because the prominent pitches, F in the high melody and F-sharp in the bass, are the only two of all twelve tones that have not yet been played.
Then the bass adds another dimension to the tritone, as its part is written in the key of F-sharp, against the general key of C. The final note heard before the gangs start fighting, is the E natural, an example of the lowered seventh.
The Prologue is filled with its tension through Bernstein's use off dissonant, chromatic, syncopated notes.
"If there was a Mount Rushmore for Broadway scores, "West Side Story" would be front and center. It snaps, it crackles it pops! It surges with a roar, its energy and sheer life undiminished by the years" - NYPost reviewer Elisabeth Vincentelli